A new source of everyday energy: piezoelectricity
Energy powers countless aspects of our daily lives, from daily amenities to the technologies we use. But, as these technologies shift and evolve, so do their energy needs.
One of these evolving technologies is the Internet of Things (IoT), which refers to anything that uses sensors to transmit data across connected devices over the Internet, or other communications networks. From automatic door locks to smartphones, the IoT is a rapidly growing facet of modern life. Conventional batteries are still used to power these devices, but their bulky size is incompatible with small IoT sensors, and charging and tracking batteries’ lifetimes is an additional burden. Millions of single-use batteries power IoT devices every day, generating large amounts of waste. As such, alternative sources of energy are needed for a sustainable future. These can be accessed through energy harvesting, or the process of deriving energy from external sources – otherwise known as ambient energy.
One form of ambient energy is mechanical energy, which can be harvested using the piezoelectric effect- electricity is generated when mechanical pressure is exerted on certain materials. Among various energy harvesting methods, piezoelectricity is a well-matured and comparatively easy method with high power conversion efficiency. Raja Sekhar Muddam is completing his PhD in the School of Physics and Astronomy as part of the Energy Harvesting Research Group: a collective working toward providing clean, affordable and secure energy through combining material-focused innovation with emerging technology such as IoT. Muddam’s research focuses on finding highly efficient and affordable materials for ambient piezo energy harvesters, to source wireless power sensors or low-powered electric components.
The advantages of replacing conventional batteries with piezoelectric devices are extensive. Pacemakers, for example, could be powered by mechanical pressure from the heart’s movements on the piezoelectric device, rather than the current mechanism of monitoring and constant battery replacement. This would reduce waste and produce a more consistent source of power for the pacemaker A wide range of piezoelectric applications is illustrated in the figure below
Harnessing this energy for consistent and widespread use requires a material that can withstand repeated mechanical pressure to generate piezoelectricity. Inorganic and oxide materials produce a high level of energy but are brittle and break easily. Organic materials are very flexible but produce less energy. To counter this issue, Muddam has identified an alternate category of material: hybrid perovskites. As a ‘hybrid’ material, it retains benefits of both organic and inorganic properties, making it suitable for generating piezoelectricity over a long period of time.
Another benefit of this hybrid perovskite material is that it is solution-processed, meaning it is produced by a combination of chemical solutions. This is a far simpler processing method than conventional piezoelectric materials which often require high temperature processing. Additionally, solution processing allows the material to be formed into a thin film, which has additional benefits of scaling up by the printing process and can be more easily integrated into electronic devices.
The final stage of the project is to integrate these hybrid perovskite-based piezoelectric devices into IoT technologies. Currently, Muddam’s piezoelectric devices can produce 2.5-4 Volts, enough to power low powered wireless sensor (such as humidity and temperature sensor) in the IoT system. Muddam and the team are also investigating different sources of mechanical pressure to power the devices, from flexible screens on computers and phones to building the devices into shoes. Currently, the piezoelectric devices are limited to 2 cm2 for integration into small-scale IoT technologies. However, as the team becomes more familiar with these methods